An electronic oscillation circuit provides an oscillating electric output signal, often in response to a control signal that adjusts one or more characteristics of the oscillating electric output signal. An electronic oscillation circuit can include, for example, a voltage-controlled oscillator (VCO) circuit, or a current-controlled oscillator circuit. Oscillating electric output signal characteristics can include, among others, signal amplitude, frequency, or waveform morphology.
In an example, a voltage-controlled oscillator provides an oscillating electric output signal determined, at least in part, by a voltage control input signal. For instance, an amplitude of a voltage control input signal can correspond to a frequency of the oscillating electric output signal, and a change in the amplitude of the voltage control input signal can correspond to a change in the frequency of the oscillating electric output signal. In other examples, an electronic oscillation circuit can be controlled by a current control input signal, such that a change in the current control input signal corresponds to a change in the frequency of the oscillating electric output signal.
Some examples of signals that can be generated by electronic oscillation circuits include processor clock signals, signals configured for wired and wireless communications, system synchronization signals, and audio signals, among others. VCOs are used in control systems, such as in phase-locked loop (PLL) circuits. In an example, a PLL circuit includes a PLL output that is fed back to a PLL input, and a reference input. The PLL output signal has a phase that is generated using a VCO and is based on a comparison of a reference signal phase and the PLL output signal phase.